1. Field of Disclosure
This disclosure relates in general to wellhead assemblies, and in particular to wellhead assembly members for providing control of wellhead assembly operations.
2. Description of Related Art
Some conventional subsea wellhead assemblies include a high pressure wellhead housing that supports one or more casing hangers located at upper ends of strings of casing extending into the well. A tubing hanger lands in the wellhead housing above the casing hanger and supports a string of production tubing that extends through the smallest diameter casing. The tubing hanger has a production bore which is offset slightly from the longitudinal axis. An annulus bore also extends through the tubing hanger, parallel to and offset from the axis, for communicating the tubing annulus to above the tubing hanger. The annulus bore is needed during installation of the tubing hanger and tubing to establish circulation down the tubing and back up the annulus. After the well has been completed, a removable plug is installed in the annulus bore, then a production tree is mounted to the wellhead housing. Access through the production tree to the tubing may be made for various workover operations that are needed. Various production valves and chokes will be mounted to the tree. Typically the bore of a subsea wellhead is limited, and may be for example, 18-¾ inches. Having both a production line and annulus bore traveling through the wellhead assembly constrains the sizes of production tubing that can be used, and limits the number of well controls and monitoring lines that can be included within the wellhead.